The present invention relates to a steel laminate gasket for an internal combustion engine, more particularly improved steel laminate gasket which can seal properly between two engine blocks of the engine.
In the steel laminate gasket, one of the very important things when the steel laminate gasket is designed is how portions around holes of the engine are securely sealed. If the portions around the holes of the engine is not properly sealed, the engine can not operate as intended. In this respect, there have been proposed many methods.
One conventional steel laminate gasket 20 is shown in FIG. 1, wherein the gasket 20 comprises an upper plate 21, a lower plate 22, a middle plate 23, and a middle plate 24 having a bead 25 around a hole 26 to be sealed. The lower plate 22 is provided with a curved portion 27 located around the hole 26, and an edge portion 28 situated above the upper plate 21. In the gasket 20, a periphery of the hole 26 between two engine blocks is surrounded and sealed by the curved portion 27.
Another conventional steel laminate gasket 30 is shown in FIG. 2, wherein the gasket 30 comprises an upper plate 31, a lower plate 32, a middle plate 33, a middle plate 34 having a bead 35 around the hole 26 to be sealed, and a cylindrical member 36. The cylindrical member 36 includes an upper portion 37 situated above the upper plate 31, a lower portion 38 situated below the lower plate 32, and a curved portion 39. In the gasket 30, a periphery of the hole 26 between the two engine blocks is surrounded and sealed by the curved portion 39 of the cylindrical member 36.
In the gasket 20, the curved portion 27 of the lower plate 22 has to be bent when assembled, while in the gasket 30, the curved portion 39 of the cylindrical member 36 must be bent as well when assembled together. Namely, in the gaskets 20, 30, metal bending procedure is required. Therefore, in case a hole to be sealed is small, configuration of the hole is complicated or metal quality relative to bending is not good, curved or bending portions may be cracked.
In the above conventional gaskets, the curved or bending portions constitute sealing portions of the gaskets. Therefore, if the curved or bending portions have cracks therein, sealing ability of the gasket decreases, and actually, the gasket can not be used any more. When the curved or bending portions are employed in the gaskets, cracks must not be formed in the curved or bending portions. In order to satisfy this requirement, the curved or bending portion must only be utilizeded in a gasket for sealing a hole which satisfies some requirement, i.e. size and configuration of the hole. Namely, the curved or bending portion can not be utilized for a small hole or a hole with complicated configuration.
When the curved or bending portion can not be employed in a gasket, a gasket 40 as shown in FIG. 3 is used. The gasket 40 comprises a seal ring 41 situated around the hole 26 to be sealed, and a body portion 42 for supporting the seal ring 41. The seal ring 41 includes a rubber ring portion 43, and a supporting plate 44 engaging the ring portion 43. The body portion 42 includes an upper plate 45, a lower plate 46, and two middle plates 47. A lateral depression 48 is formed between the upper and lower plates 45, 46 adjacent to the middle plates 47. A part of the plate 44 is situated in the depression 48 so that the seal ring 41 is engaged with the body portion 42.
When the seal ring 41 is employed, the structure of the gasket becomes complicated. Also, manufacturing cost of the gasket becomes expensive because of using an expensive heat resisting rubber. Further, quality of rubber goes wrong as time goes by. Therefore, the gasket 4o is not satisfactory.
When the curved or bending portion is not used, a gasket 50 as shown in FIG. 4 may also be used. The gasket 50 comprises an upper plate 51, a lower plate 52 and a middle plate 53 having a bead 54 around the hole 26, wherein a portion abutting against the hole 26 is not covered. In this case, the structure of the gasket 50 is simple, but fluid passing through the hole 26 may possibly penetrate through the plates of the gasket 50. Sealing ability of the gasket 50 is not good.
Accordingly, one object of the present invention is to provide a steel laminate gasket which can seal properly even in a small hole or a hole with complicated configuration.
Another object of the invention is to provide a steel laminate gasket as explained above, which can be effectively used for a long period of time.
A further object of the present invention is to provide a steel laminate gasket as explained above, which, when used around a water hole of an engine, can restrict water flow passing through the water hole while a portion around the water hole is effectively sealed.
A still further object of the present invention is to provide a steel laminate gasket as explained above, which can be manufactured economically.
Further objects and advantages of the invention will be apparent from the following description of the invention.